1. Field of the Invention
The present invention relates to an illumination system with multiple independent loops, and more particularly to a LED illumination system with multiple independent loops.
2. Description of the Related Art
General lighting has an enormous effect in human activities and product property. Conventional general lighting includes incandescent lamp, fluorescent lamp and so on.
Since Edison improved the incandescent lamp in 1879, the incandescent lamp has been providing the low-price and convenient lighting source all the time. However, the incandescent lamp has drawbacks of low lighting efficiency, high power consumption, short life-time, heat-generating, and being easily broken. Particularly, global warming is a critical issue these days, and those drawbacks of the incandescent lamp are becoming more and more concerned by people. The fluorescent lamp is also the main device for providing indoor luminescence, and, however, still has problems of mercury contamination and high-voltage driven radiation.
The blue light LED based on GaN (Gallium Nitride) series blue light LED technology proposed by Nichia Corp., Japan, in 1996, excites YAG (yttrium aluminum garnet) phosphors to generate yellow fluorescence mixed with blue light to produce white light (blue light LED with YAG phosphors), and, therefore, the LEDs are henceforth stepping into the luminescence market.
In comparison with the conventional incandescent lamp and fluorescent lamp, the white light LED has lots of advantages such as small physical size, low heat-generating, low power consumption, long lifetime, quick response time, environmental protection, flat package, and being easily developed for light weight and small size products. As the luminescence of the LED is improved and the LED cost downs is achieved, usages of the LED increases thereupon. Due to that the LED need to be D.C. voltage driven, if the LED wants to be applied to utility input (85Vac-264Vac) voltage usage, the corresponding driving circuits are essential.
Reference is made to FIG. 1 which is a related art LED driving circuit. The LED driving circuit 10 comprises a high voltage circuit block 20, a low voltage circuit block 30, an isolated power inverter 40, and two photo couplers 44A, 44B. The isolated power inverter 40 is connected between the high voltage circuit block 20 and the low voltage circuit block 30. A utility input voltage (85Vac˜264Vac) is inputted to an input end 20A, and the utility input voltage is sequentially processed by an EMI filtering unit 22, a bridge rectifying/filtering unit 24, and a power factor correction unit 26. The power factor correction unit 26 is controlled by a PWM unit 28. The power factor correction unit 26 outputs a voltage, and the outputted voltage is lowered by the isolated power inverter 40 to provide a desired voltage level, such as 24 volts. The low voltage circuit block 30 processes an outputted voltage of the isolated power inverter 40. The low voltage circuit block 30 includes a low voltage rectifying unit 32, a LC filtering unit 34, and an output unit 36. A digital-analog converter (DAC) (now shown) is built in the isolated power inverter 40 to convert a D.C. voltage outputted from the power factor correction unit 26 to a A.C. voltage, and the converted A.C. voltage is transformed into a lower A.C. voltage.
The LED driving circuit 10 further comprises a first feedback path 46A and a second feedback path 46B. The first feedback path 46A is connected between the low voltage rectifying unit 32 and the LC filtering unit 34, and the second feedback path 46B is connected between the LC filtering unit 34 and the output unit 36. The first feedback path 46A and the second feedback path 46B are connected to the photo coupler 44A and the photo coupler 44B, respectively, and provide feedback signals to the photo couplers 44A, 44B. In addition, the LED driving circuit 10 further comprises an auxiliary power source 42 to provide desired power to the PWM unit 28.
In addition, the multiple LEDs are mutually influenced when the multiple LEDs are simultaneously driven by the LED driving circuit 10.
Furthermore, it is desirable to integrate a low energy-consuming LED illumination apparatus with solar energy to reduce demand of the utility power because environment protection and energy saving were paid much attention recently. Furthermore, lighting efficiency will increase when the LED illumination apparatus is optimally controlled according to surrounding environmental light and temperature.